We set out to determine associations between hospitalization and disease severity before and 2 hours after initiation of asthma therapy in the Emergency Department, and to describe the outcome of patients admitted and discharged. This is a retrospective review of data and charts from a randomized, double blind, placebo-controlled trial (R.C.T.) of 120 asthmatics 5-17 years of age with baseline forced expiratory volume in 1 second (FEV1) < 50% predicted, treated with 3 or 1 or 0 doses of nebulized ipratropium added to three albuterol nebulizations administered over 1 hour. None of the clinical parameters measured at baseline were associated with hospitalization. However, by 2 hours after initiation of therapy, both the FEV1 percent of predicted values (% pred.) and the total asthma score were associated with likelihood of hospital admission. Baseline O2 saturation < 92% indicated a longer hospital stay (75.3 +/- 51 hours vs. 43.0 +/- 24.4 hours, P = 0.015) and a later onset of infrequent nebulizations (46.7 +/- 35.1 vs. 26.6 +/- 17.4 hours, P = 0.006). By 2 hours, those with a post-treatment FEV1 % pred < or = 30% and an asthma score > or = 6 of 9 had a high likelihood of hospitalization (86 and 80%, respectively, combined probability 100%), whereas FEV1 % pred > or = 60% and total asthma score < 3 were associated with successful discharge (probability of 92 and 83%, respectively). We conclude that pre-treatment assessments were not associated with hospitalization, while patients with post-treatment FEV1 % pred < or = 30% and a score > or = 6 had high likelihood of hospitalization.